Scatter plots in MATLAB - Step-by-Step Execution

Concept Flow - Scatter plots

Prepare data vectors X and Y

↓

Call scatter(X, Y)

↓

Plot points on graph

↓

Customize plot (color, size, labels)

↓

Display scatter plot window

Scatter plots show points on a graph using X and Y data vectors, then customize and display the plot.

Execution Sample

MATLAB

X = [1, 2, 3, 4];
Y = [10, 15, 13, 17];
scatter(X, Y, 'filled');
title('Simple Scatter Plot');
xlabel('X axis');
ylabel('Y axis');

This code creates a scatter plot of four points with filled markers and labels the axes and title.

Execution Table

Step	Action	Data State	Plot State	Output
1	Create X vector	X = [1 2 3 4]	No plot yet	No output
2	Create Y vector	Y = [10 15 13 17]	No plot yet	No output
3	Call scatter(X, Y, 'filled')	X and Y unchanged	Points plotted at (1,10), (2,15), (3,13), (4,17) with filled markers	Scatter plot points visible
4	Add title	Data unchanged	Title set to 'Simple Scatter Plot'	Title displayed on plot
5	Add xlabel	Data unchanged	X axis labeled 'X axis'	X axis label visible
6	Add ylabel	Data unchanged	Y axis labeled 'Y axis'	Y axis label visible
7	Display plot window	Data unchanged	Complete scatter plot shown	Graph window visible with points and labels

💡 All commands executed, scatter plot fully displayed

Variable Tracker

Variable	Start	After Step 1	After Step 2	Final
X	undefined	[1 2 3 4]	[1 2 3 4]	[1 2 3 4]
Y	undefined	undefined	[10 15 13 17]	[10 15 13 17]

Key Moments - 3 Insights

Why do the points appear only after calling scatter(X, Y)?

Because creating vectors X and Y only stores data; the scatter function actually draws the points on the plot (see execution_table step 3).

What does the 'filled' option do in scatter(X, Y, 'filled')?

It fills the markers with color instead of just showing outlines, making points easier to see (refer to execution_table step 3).

Why do we add title, xlabel, and ylabel after scatter?

These commands add labels and titles to the existing plot for clarity, enhancing the plot after points are drawn (see steps 4-6).

Visual Quiz - 3 Questions

Look at the execution_table at step 3, what is the state of the plot?

A No points plotted yet

B Only axes labels are set

C Points plotted with filled markers

D Plot window closed

💡 Hint

Check the 'Plot State' column at step 3 in execution_table

At which step does the X axis label appear on the plot?

A Step 5

B Step 3

C Step 2

D Step 7

💡 Hint

Look for 'X axis labeled' in the 'Plot State' column in execution_table

If we remove the 'filled' option from scatter, what changes in the plot?

A Points become larger

B Points are hollow (not filled)

C Plot title disappears

D X and Y vectors change

💡 Hint

Recall the explanation in key_moments about the 'filled' option

Concept Snapshot

Scatter plots in MATLAB:
- Use scatter(X, Y) to plot points from vectors X and Y.
- 'filled' option fills markers with color.
- Use title(), xlabel(), ylabel() to add labels.
- Points appear only after scatter() is called.
- Customize plot after points are drawn.

Full Transcript

This visual execution shows how MATLAB creates a scatter plot step-by-step. First, vectors X and Y are created to hold data points. Then, scatter(X, Y, 'filled') draws the points on the graph with filled markers. After that, title, xlabel, and ylabel commands add labels to the plot for clarity. The plot window finally displays all these elements together. Key moments include understanding that data vectors alone do not show points until scatter is called, and the 'filled' option changes marker style. The quiz questions help check understanding of plot state at each step and the effect of options.